Fix #324840: Ctrl+Scrollwheel zoom on Linux X11

With recent libinput versions zooming with Ctrl+Scrollwheel would zoom
in huge steps. This change enforces the previous behavior for Linux X11
only.

Scrolling is left unchanged for Wayland

src/notation/view/notationviewinputcontroller.cpp

@@ -398,6 +398,15 @@ void NotationViewInputController::wheelEvent(QWheelEvent* event)
     qreal stepsX = 0.0;
     qreal stepsY = 0.0;
 
+// pixelDelta is unreliable on X11
+#ifdef Q_OS_LINUX
+    if (std::getenv("WAYLAND_DISPLAY") == NULL) {
+        // Ignore pixelsScrolled unless Wayland is used
+        pixelsScrolled.setX(0);
+        pixelsScrolled.setY(0);
+    }
+#endif
+
     if (!pixelsScrolled.isNull()) {
         dx = pixelsScrolled.x();
         dy = pixelsScrolled.y();